1. Technical Field
The present disclosure relates to a navigation satellite system, an electronic device, a transmitter, and positioning method that receive a radio wave from a global navigation satellite system (GNSS) satellite such as a global positioning system (GPS) satellite and calculate position coordinates.
2. Description of the Related Art
A GPS is a navigation satellite method for performing three-dimensional detection on the earth based on positions of twenty-four satellites that rotate above the earth. One example of the GPS is a kinematic positioning method. The kinematic positioning method is a method for calculating an error based on a radio wave (a carrier wave) received by a fixed station (a base station) whose position coordinates have been known (an electronic reference point), and transmitting the calculated error to a mobile station (an electronic device) to improve accuracy of navigation in the mobile station. A developed positioning method of the kinematic positioning method is a real time kinematic positioning method for navigating a mobile station in real time (hereinafter, referred to as an RTK positioning method). In the RTK positioning method, position coordinates are obtained by using a difference in a wave number (a number of waves) of carrier waves (radio waves) transmitted from the GPS satellite to the earth. However, in order to perform the RTK positioning method, a radio wave from a GPS satellite should be received in a mobile station whose position coordinates are to be obtained. Therefore, the RTK positioning method cannot be performed in a place such as under a bridge, where a radio wave cannot be received from the GPS satellite.
Unexamined Japanese Patent Publication No. 10-213644 (1998) discloses a man location system that estimates a current position through three-point survey calculation among base station estimated positions of personal handyphone system (PHS) base stations and a pseudo distance due to electric field strength when a radio wave from a GPS satellite cannot be received.